The search can be performed for single words like Observation or Format or for a phrase which must be surrounded by double quotes "ICQ Observation Format". The main difference is that the phrase syntax searches for terms in the same order. The default operator is AND which means that all terms must be present.
The preferred operators are + (this term must be present) and - (this term must not be present).
For example, this query:
ICQ -format states that: